Collect. Czech. Chem. Commun. 1988, 53, 2843-2853

Conformation of branched polypeptides: The influence of relative position of leucine residues in the side chains

Gabor Mezőa, Hana Votavováb, Ferencz Hudeczc, Judit Kajtárc, Jaroslav Šponarb and Mária Szekerkea

a Research Group for Peptide Chemistry, Hungarian Academy of Sciences, Muzeum krt 4/B, H-1088 Budapest, Hungary
b Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6, Czechoslovakia
c Institute of Organic Chemistry, L. Eötvös University, Budapest, Hungary


Branched polypeptides were synthesized with the general formula poly(Lys-(Xi)) or poly(Lys-(DL-Alam-Xi)), where X = Leu or D-Leu, i < 1, 1 < m < 2. Coupling of Leu or D-Leu to poly(Lys) was achieved by the active ester method. The short DL-Ala oligomers were joined to the side chains by polymerisation of N-carboxy-DL-Ala anhydride. The CD measurements performed in water solutions of various pH and ionic strength indicated that joining Leu or D-Leu directly to Lys ε-amino groups increases dramatically the helix forming tendency. However, this ability was somewhat less pronounced with the D-enantiomer of Leu in accordance with our previous observations concerning the role of configuration. The polypeptide with short DL-Ala oligomers as outside determinants was investigated extensively even in trifluoroethanol-water mixtures and SDS solutions. No significant conformational influence could be demonstrated by the elongation of the branches with 1-2 DL-Ala residues.